산업용 방사선원에 대한 개선된 차폐평가 방법론 개발 = Development of Improved Methodology for Shielding Evaluation of Industrial Radiation Sources

다국어 초록 (Multilingual Abstract)

X-ray-generating devices (XGDs) and gamma-ray-emitting radioactive isotopes (RI) are widely utilized across various industrial sectors for product defect inspection, security screening, food inspection, compositional analysis, thickness and level gauges, and radiation sterilization. Accordingly, the importance of ensuring radiation safety in their use has been continuously emphasized. The shielding evaluation methods currently used in industrial practice rely on outdated experimental data and exhibit inconsistencies across references, highlighting the need for improvements.
The objectives of this study are (1) to re-evaluate the validity of data presented in NCRP Report No. 49 (NCRP 49), which has long been used as a shielding evaluation reference for industrial XGDs, and to propose an improved shielding evaluation methodology suitable for industrial XGDs operated in constant-potential mode; and (2) to quantitatively analyze the radiological and shielding characteristics of 192Ir, the most widely used RI in industrial radiography, thereby establishing a reliable shielding evaluation methodology.
In the case of XGDs, the major provisions of NCRP 49 were first reviewed, followed by measurements of dose rates under various tube voltage conditions (100–320kV) as a function of lead thickness. The Raysafe 452 dose-rate meter was used in the experiments, and the measured data were formulated to derive, for each tube voltage, the HVL corresponding to the most hardened radiation quality. The lead thickness required to achieve a dose rate of 10μSv/h at a distance of 1m from the target was compared with existing data, revealing discrepancies of up to 16.16% from the NCRP 49 method.
In the case of 192Ir, the effects of source configurations and usage conditions on shielding performance were analyzed using the MCNP6.2 code. The results showed that the gamma constant exhibited discrepancies of up to 40.4% relative to values reported in the reference. The HVLs were evaluated to be 3.32–5.51mm for lead, 13.39–25.42mm for steel, and 4.43–6.91cm for concrete.
The present study systematically verified and improved shielding evaluation methods for industrial XGDs and 192Ir. These advancements are expected to enhance the reliability and consistency of shielding evaluations from a regulatory perspective and to make a substantive contribution to improving radiation safety in practical applications.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• Chapter 2. Shielding Evaluation Method for Industrial XGDs 4
• 2.1 Radiological Characteristics 4
• 2.2 Existing Shielding Evaluation Methods 13
• 2.2.1 Primary Radiation 15
• 2.2.2 Scattered Radiation 20
• 2.2.3 Leakage Radiation 23
• 2.2.4 Limitations 25
• 2.3 Improved Evaluation Method for Primary Radiation 27
• 2.3.1 Selection of XGD and Dose-rate Meter 27
• 2.3.2 Experimental Conditions 37
• 2.3.3 Improved Evaluation Method 40
• 2.4. Improved Evaluation Method for Stray Radiation 53
• 2.4.1 Scattered Radiation 53
• 2.4.2 Leakage Radiation 60
• Chapter 3. Shielding Evaluation Method for 192Ir 61
• 3.1 Radiological Characteristics and Shielding Evaluation Methods 61
• 3.1.1 Radiological Characteristics and Source Configurations 63
• 3.1.2 Shielding Evaluation Method 67
• 3.1.3 Conditions for Monte Carlo Calculations 70
• 3.2 Improved Applicability of Gamma Constants 72
• 3.3 Improved Applicability of HVLs 79
• 3.3.1 Effect of Beam Conditions 88
• 3.3.2 Improved Shielding Evaluation for Lead 91
• 3.3.3 HVLs for Different Shielding Materials 94
• Chapter 4. Conclusion 96